Spray cleaning method for removing oil,grease,dirt and embedded oxides from painted surfaces



United States Patent 3,494,795 SPRAY CLEANING METHOD FOR REMOVING OIL,GREASE, DIRT AND EMBEDDED OXIDES FROM PAINTED SURFACES Edward H. Chang,Minneapolis, Minn., assignor to Fremont Industries, Inc., Minneapolis,Minn., a corporation of Minnesota No Drawing. Filed Aug. 7, 1967, Ser.No. 658,623 Int. Cl. B08b 3/04; C23g 1/02; C09k 3/00 US. Cl. 13440Claims ABSTRACT OF THE DISCLOSURE Oil, grease, dirt and embedded oxidesare removed from a painted metallic surface without adversely affectingthe painted surface by applying an aqueous solution thereto in a highpressure spray, the solution consisting essentially of, within certainproportions, sulfuric acid, hydrofluoric acid, a sugar derivedcarboxylic acid selected from the group consisting of gluconic andglucoheptonic acids, a water soluble glycol ether, a wetting agent, andwater.

A cleaning composition specifically adapted for use in cleaning paintedmetal surfaces such as railroad cars, railroad engines, wheel supporttrucks and the like, the composition being particularly designed for usewith high pressure spray cleaning techniques wherein the compositiondevelops a special froth of foam along the surfaces of the member beingcleaned.

The present invention relates generally to a method and composition forperforming cleaning, restoring, or other similar operations on paintedsurfaces or the like, and more particularly to a technique for cleaningand restoring the painted metal surfaces of high speed vehicles havingsoil embedded in hydrocarbons and other difiicultly removablesubstances. These surfaces are found on vehicles such as railroad cars,railroad engines, wheel support trucks and the like wherein the surfacesoil is normally heavy, and is frequently combined with hydrocarbon oilsor greases. In accordance with the present invention, a treatmenttechnique and composition is available which removes the soilexpeditiously, and restores the painted surface to a substantially newlypainted appearance without having any substantial deleterious effect onthe surface and without creating noxious odors or fumes in the cleaningzone.

Surfaces which are heavily weathered, highly oxidized, and embedded withsoil such as particles of silicon dioxide, calcium oxide, magnesiumoxide, and the like, such as are frequently found on the paintedsurfaces of railroad cars and the like, are extremely difiicult toclean. These conditions are essentially always complicated by thepresence of hydrocarbon base oils and greases which normally retainsubstantial quantities of soil in combination therewith. In the past, ithas been generally accepted that the surfaces of these vehicles may bemost expeditiously cleaned by means of acid cleaners utilizing citricacid, phosphoric acid, oxalic acid, sulfuric acid, hydrofluoric acid,sulfamic acid, sodium bi-sulfate and the like. These materials, asutilized, are not particularly suitable for use on hydrocarbon films.While the alkaline cleaners have certain merit in this regard, theirover-all usefulness is limited inasmuch as they are not particularlysuitable for oxide soils. The painted surfaces are therefore notrestored to their original oxide-free condition, since the embeddedoxides are not completely removed in each instance. In accordance withthe technique of the present invention, a spray cleaning compositionhaving a low pH, such as in the range of 0.7 and 3.0 is obtained whereinthe solution further contains a compound for increasing the solvency ofthe dirt retaining greases and oils, this composition being sprayed ontosurfaces to be cleaned at a high pressure in order to dissolve organicsoil and effectively penetrate and remove the dirt retaining substance.Pressures in the range of from 140 p.s.i. to about 400 psi. have beenfound to be effective, and there is a sufficient frothing actionavailable in the solution to prevent evaporation of the water andconsequent increased concentration of the acid constituents.

The acids included are preferably hydrofluoric and sulfuric, althoughany acid compound containing the H group, such as sulfonic acids or thelike may be used. Because of the economic advantages of sulfuric acid,this compound will normally be utilized. Hydrofluoric acid is includedin the composition to assist the removal of certain oxides. Because ofthe difficulties of handling hydrofluoric acid in a spray environment,this material is kept at a practical minimum in the over-all cleaningcomposition. In order to provide a streak-proof surface, a complexingagent comprising a carboxylic acid derived from a sugar derivative, suchas gluconic or glucoheptonic acid is utilized. This material has beenfound to produce a complexing action in the mixture and hence isdesirable as a component. If desired, a suitable wetting agent may beemployed in the solution used. The wetting agent functions in the normalsense, and assists in thoroughly wetting the surface in order to improvethe cleaning operation. In the technique of the present invention, asolution containing a suitable quantity of the working ingredients isapplied by high pressure spray techniques to the soiled surface. Theaction of the cleaner is suflicient, including the frothing and thecleaning action, to restore and clean the soiled surfaces withoutadversely affecting the painted metal surfaces.

Therefore, it is an object of the present invention to provide animproved technique for restoring badly weathered and soiled paintedsurfaces.

It is a further object of the present invention to provide an improvedtechnique for restoring, cleaning, and otherwise treating paintedmetallic surfaces.

It is yet a further object of the present invention to provide animproved high pressure spray treating technique for the restoration ofpainted metallic surfaces wherein an acidic cleaner is utilized.

Other and further objects of the present invention will become apparentto those skilled in the art upon a study of the following specificationand appended claims.

In accordance with the preferred modification of the present invention,a working solution is prepared from a concentrate, these mixtures havingthe following ingredients:

TABLE I Working solution, Concentrate, percent by percent by Compoundweight weight Sulfuric acid. 66 Be 0. 075-5. 0 2. Hydrofluorie acid,(activebasis 0. 400-8. 0 Gluconic Acid, 50% 0. 010-2. 5 0. 5-10Octylphenoxy poly (ethylene oxy) ethanol having 9 mols of ethylene oxide0. 030-5. 0 1. 0l5 Ethylene glycol monobutvl' Ether 0. 500-7. 5 5. 015Water Balance Balance pH 1 0. 7-3. 0

About.

cluded at a lower working limit of 0.4 percent by weight f'according toTable I above, and any lesser quantity will tend to render the solutiontoo slow to be deemed reasonably operative. An upper limit of 8.0percent of hydrofluoric acid is deemed practical in the workingsolution, this limit being imposed because of the corrosive nature ofthe substance on the surfaces being treated, and also be cause of thedifliculties encountered in the normal handling of this material duringa spraying operation. In this connection, compositions with greaterhydrofluoric acid composition may fume. While the odor of the acid mistis undesirable, it has been found that the odor may be effectivelycountered by the use of a glycol ether such as ethylene glycol monobutylether in the solution in the range of 0.5 percent or more. The wettingagent also assists in establishing a froth or foam to control theconcentration of the acid mixture subsequent to the spraying operation.

The carboxylic acids which are derived from sugar derivatives appear tofunction as an agent which prevents or eliminates streaking of thecleaned surface; and in this connection, gluconic and glucoheptonicacids have been found to be extremely desirable.

The composition includes a wetting agent which is critical to thecomposition. In this regard, octyl or nonyl phenoxy poly (ethylene oxy)ethanol may be used, the octyl material being preferred. Thecompositions include from between 7 and 13 mols of ethylene oxide permol of octyl phenol, or from between 9 and 13 mols of ethylene oxide Iper mol of nonyl phenol, and preferably 9' mols of ethylene oxide witheither octyl or nonyl phenol. The wetting agent is present in the amountranging from 0.03 to 15 percent in the composition.

The glycol ether utilized increases the solvency of the dirt retaininggreases and oils, and is accordingly used to dissolve organic soil andassist in the penetration of the hydrofluoric acid through the organicsoil layer or film. In this regard, ethylene glycol monobutyl ether ispreferred, however, other glycol ethers based on other than butylalcohol and other glycols than ethylene glycol may be utilized.Diethylene glycol and ethanol or propanol may be used. It has been foundthat ethylene glycol monobutyl ether or other water soluble glycolethers listed hereinabove together with the wetting agent assist inreducing the odor caused from the acid mist of the spray, particularlythe hydrofluoric acid odor. In this regard, the material has been foundto be extremely desirable in the product.

While the above solution has been utilized and specified generally, thefollowing table, Table 11, discloses a specific example of a preferredsolution for use in accordance with the cleaning technique of thepresent invention.

Mix with water in ratio of from 1:8 although from 1:5 up to 1:10 may beused for pH from 1.3-2.0.

It will be appreciated that the solutions indicated hereinabove may beshipped in concentrated form, and diluted at the cleaning site. In thisregard, the concentrate may be prepared in such a way that a mixture ofone part concentrate to from four parts to ten parts of water or more.may be employed. Furthermore, it has been found that for extremely lightsoil conditions, a concentrate may be utilized which is diluted morecompletely such as is found in the lower limits of the concentrationsset forth in Table I. For cases where heavy oxide conditions are found,it is generally preferable to keep the hydrogen fluoride concentrationat the higher portions of the range. While the technique is mostparticularly adapted to cleaning of heavily soiled metallic paintedsurfaces, it will be appreciated that the composition may be utilizedfor cleaning wooden painted surfaces as well.

It will be appreciated that the examples given herein are for purposesof illustration only, and there is accordingly no intention of limitingthe scope of this invention to these examples alone. Those skilled inthe art may depart from these examples without departing from the spiritand scope of the present invention.

What is claimed is:

1. The method of removing oil, grease, dirt and embedded oxide from apainted metallic surface without adversely affecting the painted surfacecomprising applying an aqueous solution thereto by means of a highpressure spray, the solution consisting essentially of sulfuric acid,hydrofluoric acid, a sugar derived carboxylic acid selected from thegroup consisting of gluconic and glucoheptonic acids, a water solubleglycol ether having a structural formula R--(OCH CH )nOH wherein R is analkyl radical containing from 1 to 4 carbon atoms, and n is an integerfrom 1 to 2, preferably 1, a wetting agent, and water, said sulfuricacid being present in an amount ranging from between about 0.075 percentand 5 percent by Weight, said hydrofluoric acid being present in anamount ranging from between about 0.4 percent to 8 percent by weight,said sugar derived carboxylic acid being present in an amount rangingfrom about 0.01 percent up to about 2.5 percent by weight, said watersoluble glycol ether being present in an amount ranging from betweenabout 0.5 percent and 10 percent by weight, and said wetting agent beingpresent in an amount ranging from between about 0.03 percent and 15percent by weight, with the remainder being water.

2. The method as set forth in claim 1 being particularly characterizedin that the spray technique employs pressures in the range of from aboutp.s.i. up to about 400 p.s.i.

3. The method of cleaning painted metallic surfaces as defined in claim2 being particularly characterized in that said water soluble glycolether is ethylene glycol monobutyl ether.

4. The method as defined in claim 3 being particularly characterized inthat said ethylene glycol monobutyl ether is present in an amountconstituting about 0.5 percent by weight of the solution.

5. The method as set forth in claim 3 being particularly characterizedin that said wetting agent has a structural formula agoomcmon-orncmonwherein R is an alkyl radical containing from 8 to 9 carbon atoms, andwherein x is a quantity ranging from between 7 and 13, and wherein saidsolution is a concentrate consisting essentially of about 3 percent byweight of said sulfuric acid, about 6 percent by weight of saidhydrofluoric acid, about 1.2 percent by weight of said sugar derivedcarboxylic acid, about 5 percent by weight of said ethylene glycolmonobutyl ether, and about 3 percent by weight of said wetting agent'with the remainder water, said concentrate being diluted withadditional water in the range of from about 1:5 up to about ReferencesCited UNITED STATES PATENTS Neilson. Szatyn 134--40 XR McDonald 13441 XRKelly 134 3 XR MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, AssistantExaminer U.S. Cl. X.R. 1343, 34, 41

